The purpose of this research is to develop a clinically applicable time-varying three-dimensional (3-D) reconstruction of the in vivo left ventricle from two-dimensional (2-D) echocardiograms which would accurately characterize the geometric changes in the chamber and wall during a cardiac cycle. The reconstruction realigns five 2-D echo cross-sections on the long axis. Spacial registration is achieved using a mechanical arm with 5 degrees of freedom. Studies performed during the first year of the grant have included: 1. Four new patient studies. 2. Calibration and determination of the accuracy of the spacial registration arm. 3. 2-D beam shape experiments. 4. Development of volume algorithms. 5. Experiments on fixed canine and porcine hearts to verify diameter, circumference, area, and volume calculations. 6. Development of border recognition software for moving edge extraction. The patient studies have shown a great deal of variation compared to volume data obtained at the time of cardiac catheterization. While accumulation of patient data is desirable, manual techniques to digitize the heart borders are not satisfactory. If the system is to provide accurate data for patient evaluation it will require a rapid automated method to obtain reliable objective cardiac borders. Further development of border recognition programs will require accurate raw data from on-line analog-to-digital conversion (ADC) of the 2-D echo signal. Thus, in the next year, emphasis will be placed on direct ADC into our dedicated computer system. This will be accompanied by development of border recognition software and the evaluation of this software in both pulsating balloons and isolated heart experiments.